Formation of Latex Coagulum Composite for Tire Composition

ABSTRACT

A tire comprising a rubber composition based on at least an elastomer composite formed by the method of flowing a coagulating mixture of a first elastomer latex comprising a first elastomer and a particulate filler slurry along a conduit; and introducing a second elastomer latex comprising a second elastomer into the flow of the coagulating mixture.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 13/497,034filed Jul. 23, 2012 which claims the priority under 35 U.S.C. 371 ofInternational application No. PCT/US2010/002518 filed Sep. 16, 2010.Priority is also claimed of U.S. Provisional Application Nos. 61/276,876filed Sep. 17, 2009 and 61/280,453 filed Nov. 4, 2009, the entirecontents of all of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to the introduction of additional elastomer latexinto a latex coagulum composite, more particularly this inventionconcerns tire comprising rubber composition based on such elastomercomposite,

DESCRIPTION OF THE RELATED ART

In order to obtain the optimum reinforcement properties imparted by afiller in a tire tread and thus high wear resistance, it is known thatthis filler should generally be present in the elastomeric matrix in afinal form which is both as finely divided as possible and distributedas homogeneously as possible. Now, such conditions can only be obtainedinsofar as this filler has a very good ability firstly to beincorporated into the matrix during mixing with the elastomer and to bedisagglomerated, and secondly to be dispersed homogeneously in thismatrix.

Since fuel economies and the need to protect the environment have becomepriorities, it has proved necessary to produce tires having reducedrolling resistance, without adversely affecting their wear resistance.To improve the dispersion of filler into the elastomeric matrix,numerous solutions have been proposed, some of them proposing the use ofmasterbatches including elastomer and filler.

It is common to produce a masterbatch, that is, a premixture of filler,elastomer and various optional additives, such as extender oil. Carbonblack masterbatch, for example, is prepared with different grades ofcommercially available carbon black which vary both in surface area perunit weight and in structure, which describes the size and complexity ofaggregates of carbon black formed by the fusion of primary carbon blackparticles to one another.

There are a variety of methods for producing carbon black masterbatch.In one method, disclosed in U.S. Pat. No. 6,841,606 (“the '606 patent”),a carbon black slurry and an elastomer latex are combined in a vat andthen coagulated by the addition of a coagulant, such as an acid. In avariation of this process, disclosed in Japanese Patent Publication No.2005220187, natural rubber latex is diluted to 20% rubber content (fromabout 24% rubber) and combined with a protease to cleave amide bonds thenon-rubber components of the latex. The cleavage is believed to improvethe performance of the final rubber product. In another method,disclosed in U.S. Pat. No. 6,048,923, the contents of which areincorporated by reference herein, a continuous flow of a first fluidincluding an elastomer latex is fed to the mixing zone of a coagulumreactor. A continuous flow of a second fluid including a carbon blackslurry is fed under pressure to the mixing zone to form a mixture withthe elastomer latex. The mixing of the two fluids is sufficientlyenergetic to substantially completely coagulate the elastomer latex withthe carbon black prior to a discharge end of the coagulum reactor. Asdisclosed in U.S. Pat. No. 6,075,084, additional elastomer may be addedto the material that emerges from the discharge end of the coagulumreactor. As disclosed in U.S. Pat. No. 6,929,783, the coagulum may thenbe fed to a dewatering extruder.

At high loadings of carbon black, the coagulum emerges from the coagulumreactor not as a continuous flow of carbon black-elastomer composite butas a plurality of discrete carbon black-elastomer composite regionscarried by a substantially coagulum-free aqueous phase. Generally, sucha discontinuous material does not pass as easily through the dewateringextruder and can backflow within the dewatering extruder, causingclogging. It is therefore desirable to prepare a continuous flow ofcoagulum containing a high volume fraction of carbon black that can bemore easily handled in an apparatus such as a dewatering extruder.

Moreover, surprisingly we discover that tire comprising rubbercompositions based on elastomer composite having high volume fraction offiller and in particular of carbon black, present improved properties(notably processability, reinforcement, vulcanized kinetic) compared toalready improved properties of tire comprising rubber composition basedon elastomer composite having lesser volume fraction of the same fillerprepared by the method described in U.S. Pat. No. 6,048,923.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed to a process formanufacturing a rubber composition for tire, comprising the steps of a)manufacturing a coagulated latex composite by the method comprising a1)flowing a coagulating mixture of a first elastomer latex comprising afirst elastomer and a particulate filler slurry along a conduit, whereinthe particulate filler comprises a carbon black having a dibutylphthalate adsorption greater than 60 mL/100 g, and wherein the carbonblack has a surface area and is present in the coagulated latexcomposite in an amount satisfying L≧−0.26*S+94, where L is the amount ofthe carbon black in the coagulated latex composite in parts per hundredof rubber (phr) and S is the surface area in m²/g as measured by STSA;and a2) introducing a second elastomer latex comprising a secondelastomer into the flow of the coagulating mixture to obtain acoagulated latex composite in a form of coherent coagulum and the secondelastomer latex is not decorated with filler particles prior to theintroduction step; b) dewatering the coagulated latex composite obtainedin step a) into a desired water content c) incorporating all theconstituents of the composition for tire, including the dewateredcoagulated latex composite obtained in step b), in a mixer bythermomechanically kneading the whole mixture at high temperature, up toa maximum temperature of between 130° C. and 200° C., then d) performingmechanical working of the resulting mixture, with incorporation of acrosslinking system, at a temperature of less than 120° C.

Another aspect of the invention relates to a tire or tire treadcomprising a rubber composition based on at least one elastomercomposite formed by a method, comprising flowing a coagulating mixtureof a first elastomer latex comprising a first elastomer and aparticulate filler slurry along a conduit; and introducing a secondelastomer latex comprising a second elastomer into the flow of thecoagulating mixture.

The tire or tire tread made according to this method may be formed by afurther method comprising, before flowing the coagulating mixture,generating the coagulating mixture by feeding a continuous flow of thefirst elastomer latex to a mixing zone of a coagulum reactor defining anelongate coagulum zone extending from the mixing zone to a discharge endand comprising the conduit, and feeding a continuous flow of a fluidcomprising particulate filler under pressure to the mixing zone of thecoagulum reactor to form the coagulating mixture.

The tire or tire tread made according to this method may be formed by afurther method comprising steps wherein the continuous flow of the fluidcomprising particulate filler has a velocity from about 30 m/s to about250 m/s, the continuous flow of the first elastomer latex has a velocityof at most about 10 m/s, and a residence time of the coagulating mixturein the coagulum reactor before introducing the second elastomer latex isfrom 1×10⁻² s to about 6×10⁻² s.

The tire or tire tread made according to this method may be formed by afurther method comprising steps wherein the conduit comprises a firstconduit portion having a first diameter, a second conduit portion havinga second diameter greater than the first diameter, and a transition zonetherebetween having a diameter that increases from the first diameter tothe second diameter, wherein flowing comprises flowing the coagulatingmixture into the second conduit portion from the first conduit portion,and introducing comprises introducing the second elastomer latex intothe coagulating mixture in the transition region.

The tire or tire tread made according to this method may be formed by afurther method comprising steps wherein flowing the coagulating mixturecomprises flowing the coagulating mixture through the transition regionunder conditions of turbulent flow.

The tire or tire tread made according to this method may be formed by afurther method comprising steps wherein the amount of the secondelastomer in the composite is from about 0.5 wt % to about 50 wt %;wherein the amount of the second elastomer in the composite is fromabout 16 wt % to about 38 wt %; wherein the second elastomer is asynthetic elastomer or natural rubber latex, and wherein the naturalrubber latex comprises field latex, latex concentrate, skim latex, or acombination of two or more of these; and, optionally, wherein acomponent of the natural rubber latex has been chemically orenzymatically modified.

The tire or tire tread made according to this method may be formed by afurther method comprising steps wherein the particulate filler comprisesa carbon black having a surface area of at least 95 m²/g as measured bySTSA and a dibutyl phthalate adsorption greater than 80 mL/100 g, andwherein the coagulated latex composite comprises at least 65 phr of thecarbon black; or wherein the particulate filler comprises a carbon blackhaving a surface area of at least 75 m²/g as measured by STSA and adibutyl phthalate adsorption greater than 60 mL/100 g, and wherein thecoagulated latex composite comprises at least 70 phr of the carbonblack; or wherein the particulate filler comprises a carbon black havinga dibutyl phthalate adsorption greater than 60 mL/100 g, wherein thecarbon black has a surface area and is present in the coagulated latexcomposite in an amount satisfying L≧−0.26*S+94, where L is the amount ofthe carbon black in the coagulated latex composite in parts per hundredof rubber (phr) and S is the surface area in m²/g as measured by STSA;or wherein the elastomer composite includes at least 10 phr of theparticulate filler.

Another aspect of the invention relates to a tire or tire treadcomprising a rubber composition based on at least one elastomercomposite formed by a method, comprising:

-   -   generating a flow of a coagulating mixture of a first elastomer        latex comprising a first elastomer and a particulate filler        slurry having a first degree of turbulence;    -   causing the first degree of turbulence to change to a second        degree of turbulence; and    -   introducing a second elastomer latex into the coagulum at a        location where the coagulum flow has the second degree of        turbulence.

The tire or tire tread made according to this method may be formed by afurther method comprising generating a flow comprises feeding acontinuous flow of the first elastomer latex to a mixing zone of acoagulum reactor defining an elongate coagulum zone extending from themixing zone to a discharge end, and feeding a continuous flow of theparticulate filler slurry under pressure to the mixing zone of thecoagulum reactor to form the coagulating mixture.

The tire or tire tread made according to this method may be formed by afurther method, wherein the continuous flow of the fluid comprisingparticulate filler has a velocity from about 30 m/s to about 250 m/s,the continuous flow of the first elastomer latex has a velocity of atmost about 10 m/s, and a residence time of the coagulating mixture inthe coagulum reactor before introducing the second elastomer latex isfrom 1×10⁻² s to about 6×10⁻² s.

The tire or tire tread made according to this method may be formed by afurther method comprising steps wherein the amount of the secondelastomer in the composite is from about 0.5 wt % to about 50 wt %;wherein the amount of the second elastomer in the composite is fromabout 16 wt % to about 38 wt %; wherein the second elastomer is asynthetic elastomer or natural rubber latex, and wherein the naturalrubber latex comprises field latex, latex concentrate, skim latex, or acombination of two or more of these; and, optionally, wherein acomponent of the natural rubber latex has been chemically orenzymatically modified.

The tire or tire tread made according to this method may be formed by afurther method comprising steps wherein the particulate filler comprisesa carbon black having a surface area of at least 95 m²/g as measured bySTSA and a dibutyl phthalate adsorption greater than 80 mL/100 g, andwherein the coagulated latex composite comprises at least 65 phr of thecarbon black; or wherein the particulate filler comprises a carbon blackhaving a surface area of at least 75 m²/g as measured by STSA and adibutyl phthalate adsorption greater than 60 mL/100 g, and wherein thecoagulated latex composite comprises at least 70 phr of the carbonblack; or wherein the particulate filler comprises a carbon black havinga dibutyl phthalate adsorption greater than 60 mL/100 g, wherein thecarbon black has a surface area and is present in the coagulated latexcomposite in an amount satisfying L≧−0.26*S+94, where L is the amount ofthe carbon black in the coagulated latex composite in parts per hundredof rubber (phr) and S is the surface area in m²/g as measured by STSA;or wherein the elastomer composite includes at least 10 phr of theparticulate filler.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described with reference to the several drawings, inwhich:

FIG. 1 is a schematic diagram of an apparatus for production of latexcoagulum composite according to an exemplary embodiment of theinvention.

FIG. 2 is a schematic diagram of an apparatus for injection of a secondelastomer latex into a coagulum according to an exemplary embodiment ofthe invention.

FIG. 3 is a graph comparing the highest loading of carbon blacksachieved during production of elastomer composites with secondary latexaccording to an exemplary embodiment of the invention (squares) andwithout secondary latex (diamonds), as a function of surface area(STSA).

FIG. 4 is a graph showing the relationship of the highest loading ofN234 carbon black achieved with respect to residence time for productionof elastomer composite according to various embodiments of the invention(square—production rate from 450-500 kg/hr (dry basis);diamond—production rate from about 200-275 kg/hr (dry basis, based onprimary latex and carbon black only)).

DETAILED DESCRIPTION OF THE INVENTION

While it is often desirable to produce elastomer composite with higherloadings of fillers such as carbon black in a continuous wet masterbatchprocess, coagulated rubbers containing higher loadings of filler aresometimes difficult to pass through downstream processing equipment. Wehave unexpectedly discovered that adding additional elastomer latex intoa coagulating mixture having a high weight fraction of filler results inthe formation of a continuous masterbatch crumb, termed a “coherentcoagulum. Because the coherent coagulum is a cohesive mass, it does notcrumble when handled and can be easily dewatered using standardequipment such as the dewatering extruder available from the French OilMachinery Company (Piqua, Ohio, USA). This enables the continuousproduction of elastomer composites having high loadings of filler andwhich can be used to produce vulcanized rubbers having superiorproperties. In contrast, masterbatch crumb that is not cohesive canbackflow in downstream equipment, causing it to clog or to becomeineffective at de-watering.

In one embodiment, a tire comprises a rubber composition which is basedon elastomer composite formed by a method of flowing a coagulatingmixture of a first elastomer latex and a particulate filler slurry alonga conduit and introducing a second elastomer latex into the flow of thecoagulating mixture.

Accordingly, said rubber composition may be used for the tread portion,sidewalls, wire skim and/or carcass.

As shown in FIG. 1, a particulate filler slurry is fed into a mixingportion 10 of a coagulum reactor 11 via a filler feed line 12. Anelastomer latex is fed into mixing portion 10 via latex feed line 14.The latex begins to coagulate in the mixing portion 10, and thecoagulating mixture, including elastomer and particulate filler,proceeds through a diffuser portion 16 of coagulum reactor 11. As shownin FIG. 1, the diffuser portion 16 has a series of sections 18 a-18 d,each one having progressively higher diameter than the previous section18. Preferably, transition regions 20 a-c provide a gradual increase indiameter from one section 18 to the next. One of skill in the art willrecognize that the diffuser portion may have greater or fewer sections18 than shown in the figure.

The second elastomer latex, is introduced via injection system 22.Injection system 22 includes a holding tank 24 and a pump 26 thatdirects the second elastomer latex into the coagulum reactor 11 via aninjection line 28. Preferably, pump 26 is operated to generatesufficient pressure to prevent back flow of the coagulating mixture intoinjection line 28. Other suitable apparatus, e.g., different typepumping or compression equipment, may be employed to introduce thesecond elastomer latex into the coagulating mixture. As shown in FIG. 1,the second elastomer latex is injected into the coagulating mixture intransition region 20 a. One of skill in the art will recognize that theoptimal injection location for the second elastomer latex may varydepending on the composition of the coagulating mixture and the secondelastomer latex.

Elastomer latex is an emulsion of rubber particles in water. The rubberin the particles is a highly viscous fluid of rubber molecules,surrounded by a shell of naturally occurring substances that stabilizethe rubber particles against aggregation and coalescence.Destabilization of the latex causes it to coagulate, i.e, the rubberparticles aggregate and coalesce with one another. In preferredembodiments, the velocity of the particulate filler slurry issignificantly higher than that of the first elastomer latex. Theresulting high shear destabilizes the latex. Without being bound by anyparticular theory, it is believed that rapid mixing of the particulateslurry with the latex results in decoration of the rubber particlesurface by the particulates, which also destabilizes the latex. Fillerparticles colliding with each other also form agglomerates that cancollide with and destabilize latex particles. The combination of thesefactors causes the elastomer latex to destabilize; rubber particlesaggregate by forming rubber-rubber contacts or by bridging throughfiller particles on their surfaces to form rubber-filler compositeaggregates.

Without being bound by any particular theory, it is believed that in thepresence of excess particulate filler, the rubber particles or smallaggregates of rubber particles become completely decorated with thefiller, with little or no free rubber surface area to form rubber-rubbercontacts with other rubber particles. This limits the extent to whichthe rubber-filler composite aggregates can further aggregate to form acontinuous network. Instead, rather than forming a coherent coagulum,the masterbatch crumb takes the form of discontinuous composite domainsdispersed in an aqueous phase. The second elastomer latex introducesfresh latex particles that, because they are not yet decorated withfiller particles, can bind together the discrete rubber-filler compositeaggregates to form a continuous rubber-particle composite in the form ofa coherent coagulum.

For apparatus similar to that shown in FIG. 1, factors influencing thecoherence of the coagulum include the amount of particulate fillerinjected into the mixing block (e.g., the target filler loading), thefiller morphology (e.g., surface area, structure), the residence time ofthe mixture of the first elastomer latex and the particulate fillerslurry before introduction of the second elastomer latex, and theappropriate mixing of the second elastomer latex into the mixture.

According to the theory above, there is a limit beyond which theintroduction of additional latex will not enable the discreterubber-filler composite aggregates to form a coherent coagulum. That is,if there is excess filler in the mixture after the rubber particles havebeen completely decorated, the rubber particles in the second elastomerlatex stream will become decorated with the excess filler rather thanbinding the existing rubber-filler aggregates together. Thus, while theuse of the second elastomer latex stream can increase the filler loadinglevel obtainable while still producing coherent coagulum, the potentialincrease is not infinite. The concentration of the filler in the slurry,the feed rate and velocity of the filler slurry into the mixing zone,and the proportion of the rubber introduced with second elastomer latexwith respect to the total rubber in the final composite may all beoptimized to maximize the effectiveness of the second elastomer latex.

In certain embodiments, the secondary latex improves the achievablefiller loading (e.g., elastomer composite produced with this amount offiller has the morphology of a coherent coagulum) by at least 0.5 phrwith respect to elastomer composite produced in a continuous wetmasterbatch process without secondary latex, for example, from 0.5 phrto about 15 phr, from about 1 phr to about 14 phr, from about 2 phr toabout 13 phr, from about 3 phr to about 12 phr, from about 4 phr toabout 11 phr, from about 5 phr to about 10 phr, from about 6 phr toabout 9 phr, from about 7 phr to about 8 phr, from about 1 phr to about7 phr, from about 1 phr to about 6 phr, or from about 1 phr to about 5phr.

In certain preferred embodiments, use of secondary latex enables use ofa continuous wet masterbatch process to produce elastomer compositehaving at least 65 phr, for example, at least 70 phr or from 65 to 75phr, of a carbon black having a surface area of at least 95 m²/g, asmeasured by the statistical thickness method (STSA), expressed as squaremeters per gram of carbon black, according to the procedure set forth inASTM D6556 (STSA) and a structure, measured by dibutyl phthalate (DBP)adsorption (ASTM D6854), greater than 80 mL/100 g. Alternatively or inaddition, the use of secondary latex may enable use of a continuousprocess to produce elastomer composite having at least 70 phr, forexample, at least 75 phr or from 70 phr to 80 phr, of carbon blackhaving a surface area of at least 68 m²/g as measured by STSA, forexample, at least 75 m²/g, and structure, as measured by DBP adsorption,greater than 60 mL/100 g. Alternatively or in addition, use of secondarylatex enables use of a continuous wet mastermatch process to produceelastomer composite containing carbon black having a DBP adsorptiongreater than 60 mL/100 mg, for example, greater than 80 mL/100 mg,greater than 100 mL/100 mg or from 60 mL/100 mg to 160 mL/100 mg, andhaving a surface area and being present in an amount that satisfiesL≧−0.26*S−0.26*S+94, for example, L≧−0.26*S−0.26*S+97, or L≧−0.26*S+100,or L≧−0.26*S+104, or −0.26*S+94≦L≦−0.26*S+110, where L is the amount ofcarbon black in the elastomer composite in parts per hundred of rubber(phr) and S is the surface area measured as STSA (ASTM D6556), where Sis optionally greater than 65 m²/g, greater than 95 m²/g, greater than110 m²/g, or between 65 m²/g and 400 m²/g, for example between 65 m²/gand 220 m²/g, between 95 m²/g and 200 m²/g, or between 110 m²/g and 180m²/g.

Furthermore, according to the above theory, the effectiveness of thesecond elastomer latex will be maximized if it is not introduced untilsubstantially all the filler has been adsorbed onto the rubber particlesin the first elastomer latex. Otherwise, the secondary latex particlesbecome decorated with the filler rather than binding the existingrubber-filler aggregates. The time required for the filler slurry andthe elastomer latex to mix together and allow the filler particles toadsorb onto the rubber particles depends in part on how energeticallythe two fluids are mixed together. For apparatus similar to thatdepicted in FIG. 1, when the first elastomer latex is fed into mixingportion 10 at a velocity of less than about 10 m/s, for example, fromabout 1 to about 10 m/s, from about 1.5 to about 8 m/s, from about 2 toabout 6 m/s, from about 3 to about 5 m/s, or about 4 m/s to about 7 m/s,and the particulate filler slurry is fed into mixing portion 10 at avelocity of at least 30 m/s, for example, about 30 to about 250 m/s orabout 60 to about 150 m/s, a preferred residence time before injectionof the secondary latex, i.e., the time required for the mixture of theparticulate slurry to travel from the mixing portion 10 to the locationwhere the secondary latex is injected, is from about 1×10⁻² s to about6×10⁻² s, for example, from 1.5×10⁻² s to about 5.5×10⁻² s, from about1.85×10⁻² s to about 5×10⁻² s, from about 2×10⁻² s to about 4×10⁻² s,from about 2.25×10⁻² s to about 3.5×10⁻² s, from about 2.1×10⁻² s toabout 3×10⁻² s, or from about 2.25×10⁻² s to about 2.9×10⁻² s. We havealso found that excessive residence time before the introduction of thesecond elastomer latex reduces the maximum filler loading before theresulting coagulum is discontinuous rather than coherent. Without beingbound by any particular theory, this may result from incomplete mixingof the second elastomer latex into the coagulating mixture of the firstelastomer latex and particulate filler slurry, reducing theeffectiveness of the secondary latex. We have found that if the secondelastomer latex is injected too far downstream in the diffuser, it doesnot thoroughly blend into the flow of the coagulating mixture Theresidence time may be varied to optimize various operating conditions;suitable ranges may vary with the production rate.

The physical configuration of the injection system 22 also may beadjusted to optimize the mixing of the second elastomer latex into themixture. The initial flow of the coagulating mixture through theupstream portions of the diffuser is relatively turbulent. Thisturbulence gradually subsides as the coagulating mixture proceedsdownstream, and the flow of the coagulum from the outlet 34 of thediffuser is roughly laminar. Without being bound by any particulartheory, it is believed that the turbulence associated with the expansionof the flow cross-section between the first and second sections 18 a and18 b at transition 20 a facilitates mixing of the second elastomer latexinjected at that point into the coagulating rubber-filler composite.Other factors influencing mixing and turbulence include the distancefrom the point of slurry injection, the injection velocity, thedifference in cross-sectional area between the first and second diffusersections, the injection velocity of the secondary latex stream, and theangle of injection of the secondary latex stream.

For example, the second section of the diffuser 18 b may have across-sectional area from about 1.2-3.5 times the cross-sectional areaof the first section of the diffuser 18 a, for example, from about 1.2to about 1.4 times, from about 1.4 to about 1.6 times, from about 1.5 toabout 1.7 times, from about 1.7 to 1.9 times, from about 1.9 to about2.1 times, from about 2.1 to about 2.3 times, from about 2.3 to about2.5 times, from about 2.5 to about 2.7 times, from about 2.7 to about2.9 times, from about 2.9 to about 3.1 times, from about 3.1 times toabout 3.3 times, or from about 3.3 to about 3.5 times greater. Inspecific examples, the ratio of the cross-sectional areas of sections 18b and 18 a may be about 2, about 2.5, or about 3. The lengths of thevarious sections of the diffuser 18 a-18 d and the dimensions of thedownstream sections 18 c and 18 d may be as described in U.S. Pat. No.6,048,923, the contents of which are incorporated herein by reference.In certain embodiments, the length of first section 18 a may be fromabout 2 inches (5.08 cm) to about 9 inches (35.8 cm), for example, fromabout 2 inches (5.08 cm) to about 3 inches (7.62 cm), from about 3inches (7.62 cm) to about 4 inches (10.2 cm), from about 4 inches (10.2cm) to about 5 inches (12.7 cm), from about 5 inches (12.7 cm) to about6 inches (15.2 cm), from about 6 inches (15.2 cm) to about 7 inches(17.8 cm), from about 7 inches (17.8 cm) to about 8 inches (20.3 cm), orfrom about 8 inches (20.3 cm) to about 9 inches (35.8 cm). The optimallength may vary and generally increases with the production rate.

An exemplary approach for introducing the second elastomer latex to thecoagulating mixture is illustrated in FIG. 2. As shown in FIG. 2, thesecond elastomer latex is introduced into the coagulating mixture via anipple 40 that connects injection line 28 to injector 42 havinginjection orifice 42 a. An o-ring 44 may be used to improve the sealwithin nipple 40. While injector 42 is shown injecting the secondelastomer latex into the coagulating mixture at a 45 degree angle to anaxis of the coagulum reactor, one of skill in the art will recognizethat the angle and injector size may be varied depending on thecomposition of the coagulating mixture and of the second elastomerlatex. For example, when injector 42 is at a right angle to the wall oftransition area 20 a, the angle α of the transition area 20 a may befrom 0.5° to 25°, for example, from 0.5° to 1°, from 1° to 2°, from 2°to 3°, from 3° to 4°, from 4° to 5°, from 5° to 6°, from 6° to 7°, from7° to 8°, from 8° to 9°, from 9° to 10°, from 10° to 11°, from 11° to12°, from 12° to 13°, from 13° to 14°, from 14° to 15°, from 15° to 16°,from 16° to 17°, from 17° to 18°, from 18° to 19°, from 19° to 20°, from20° to 21°, from 21° to 22°, from 22° to 23°, from 23° to 24°, or from24° to 25°. In another example, the interior diameter of injectionorifice 42 a may vary from 0.045 to 0.25 inches or even larger dependingon the size of the diffuser portion 16. For example, the interiordiameter of injection orifice 42 a may be from 0.045 inches (0.11 cm) to0.055 inches (0.14 cm), from 0.055 inches (0.14 cm) to 0.06 inches (0.15cm), from 0.06 inches (0.15 cm) to 0.065 inches (0.17 cm), from 0.065inches (0.17 cm) to 0.07 inches (0.18 cm), from 0.07 inches (0.18 cm) to0.075 inches (0.19 cm), from 0.075 inches (0.19 cm) to 0.08 inches (0.20cm), from 0.08 inches (0.20 cm) to 0.09 inches (0.23 cm), from 0.09inches (0.23 cm) to 0.1 inches (0.25 cm), from 0.1 inches (0.25 cm) to0.125 inches (0.32 cm), from 0.125 inches (0.32 cm) to 0.15 inches (0.38cm), from 0.15 inches (0.38 cm) to 0.175 inches (0.44 cm), from 0.175inches (0.44 cm) to 0.2 inches (0.51 cm), from 0.2 inches (0.51 cm) to0.225 inches (0.57 cm), or from 0.225 inches (0.57 cm) to 0.25 inches(0.64 cm). One of skill in the art will recognize that the size of theinjection orifice may be varied depending, e.g., on the desired flowrate and pressure. For example, the injection pressure may be from 2-8bar (0.2-0.8 MPa), from 3-8 bar (0.3-0.8 MPa), 4-7 bar (0.4-0.7 MPa), or5-6 bar (0.5-0.6 MPa). Other suitable designs may also be employed. Forexample, the injection orifice may be gradually tapered inwardly withrespect to injector 42 or may have the same diameter as injector 42.

The second elastomer latex may have the same composition as that used toprepare the coagulating mixture, or it may differ in some way. Forexample, the second elastomer latex may be an elastomer latex from adifferent source or with a different concentration of rubber and fluid.Alternatively or in addition, it may be subjected to different chemicalmodifications (including no modification) than the first elastomerlatex.

In certain embodiments, at least one of and preferably both the firstelastomer latex (i.e., the elastomer latex in the coagulating mixture)and the second elastomer latex are prepared from a natural rubber latex.Exemplary natural rubber latices include but are not limited to fieldlatex, latex concentrate (produced, for example, by evaporation,centrifugation or creaming), skim latex (a by-product of thecentrifugation of natural rubber latex) and blends of any two or threeof these in any proportion. The latex should be appropriate for the wetmasterbatch process selected and the intended purpose or application ofthe final rubber product. The latex is provided typically in an aqueouscarrier liquid. Selection of a suitable latex or blend of latices willbe well within the ability of those skilled in the art given the benefitof the present disclosure and the knowledge of selection criteriagenerally well recognized in the industry.

The natural rubber latex may also be chemically modified in some manner.For example, it may be treated to chemically or enzymatically modify orreduce various non-rubber components, or the rubber molecules themselvesmay be modified with various monomers or other chemical groups such aschlorine. Exemplary methods of chemically modifying natural rubber latexare disclosed in European Patent Publications Nos. 1489102, 1816144, and1834980, Japanese Patent Publications Nos. 2006152211, 2006152212,2006169483, 2006183036, 2006213878, 2006213879, 2007154089, and2007154095, U.S. Pat. Nos. 6,841,606 and 7,312,271, and U.S. PatentPublication No. 2005-0148723. Other methods known to those of skill inthe art may be employed as well.

In an alternative embodiment, at least one of the first elastomer latex(i.e., the elastomer latex in the coagulating mixture) and the secondelastomer latex is prepared using synthetic latex of rubber or “diene”elastomer. The term “diene” elastomer or “diene” rubber (elastomer andrubber are well known to be synonymous terms) should be understood asmeaning, in a known way, an (one or more are understood) elastomerresulting at least in part (i.e., a homopolymer or a copolymer) fromdiene monomers (monomers carrying two carbon-carbon double bonds whichmay or may not be conjugated).

These diene elastomers can be classified into two categories:“essentially unsaturated” or “essentially saturated”. The term“essentially unsaturated” is understood to mean generally a dieneelastomer resulting at least in part from conjugated diene monomershaving a level of units of diene origin (conjugated dienes) which isgreater than 15% (mol %); thus it is that diene elastomers such as butylrubbers or copolymers of dienes and of α-olefins of EPDM type do notcome within the preceding definition and can in particular be describedas “essentially saturated” diene elastomers (low or very low level ofunits of diene origin, always less than 15%). In the category of“essentially unsaturated” diene elastomers, the term “highlyunsaturated” diene elastomer is understood to mean in particular a dieneelastomer having a level of units of diene origin (conjugated dienes)which is greater than 50%.

Synthetic diene elastomer of the first elastomer latex or of the secondelastomer latex in accordance with the invention is preferably chosenfrom the group of the highly unsaturated diene elastomers consisting ofpolybutadienes (abbreviated to “BR”), synthetic polyisoprenes (IR),butadiene copolymers, isoprene copolymers and the mixtures of theseelastomers. Such copolymers are more preferably chosen from the groupconsisting of butadiene/styrene copolymers (SBR), isoprene/butadienecopolymers (BIR), isoprene/styrene copolymers (SIR) andisoprene/butadiene/styrene copolymers (SBIR).

The elastomers can, for example, be block, random, sequential ormicrosequential elastomers and can be prepared in dispersion or insolution; they can be coupled and/or star-branched or alsofunctionalized with a coupling and/or star-branching orfunctionalization agent. For coupling with carbon black, mention may bemade, for example, of functional groups comprising a C—Sn bond or ofaminated functional groups, such as benzophenone, for example; forcoupling with a reinforcing inorganic filler, such as silica, mentionmay be made, for example, of silanol functional groups or polysiloxanefunctional groups having a silanol end (such as described, for example,in U.S. Pat. No. 6,013,718), of alkoxysilane groups (such as described,for example, in U.S. Pat. No. 5,977,238), of carboxyl groups (such asdescribed, for example, in U.S. Pat. No. 6,815,473 or US 2006/0089445)or of polyether groups (such as described, for example, in U.S. Pat. No.6,503,973). Mention may also be made, as other examples of suchfunctionalized elastomers, of elastomers (such as SBR, BR, NR or IR) ofthe epoxidized type.

The following are preferably suitable: polybutadienes, in particularthose having a content of 1,2-units of between 4% and 80% or thosehaving a content of cis-1,4-units of greater than 80%, polyisoprenes,butadiene/styrene copolymers in particular those having a styrenecontent of between 5% and 50% by weight and more particularly between20% and 40%, a content of 1,2-bonds of the butadiene part of between 4%and 65% and a content of trans-1,4-bonds of between 20% and 80%,butadiene/isoprene copolymers, in particular those having an isoprenecontent of between 5% and 90% by weight and a glass transitiontemperature (“Tg”—measured according to ASTM D 3418-82) of −40° C. to−80° C., or isoprene/styrene copolymers, in particular those having astyrene content of between 5% and 50% by weight and a Tg of between −25°C. and −50° C.

In the case of butadiene/styrene/isoprene copolymers, those having astyrene content of between 5% and 50% by weight and more particularly ofbetween 10% and 40%, an isoprene content of between 15% and 60% byweight and more particularly between 20% and 50%, a butadiene content ofbetween 5% and 50% by weight and more particularly of between 20% and40%, a content of 1,2-units of the butadiene part of between 4% and 85%,a content of trans-1,4-units of the butadiene part of between 6% and80%, a content of 1,2- plus 3,4-units of the isoprene part of between 5%and 70% and a content of trans-1,4-units of the isoprene part of between10% and 50%, and more generally any butadiene/styrene/isoprene copolymerhaving a Tg of between −20° C. and −70° C., are suitable in particular.

In some embodiments, it may be desirable to inject a coagulant, forexample, a salt or acid solution, along with the elastomer latex stream,to promote coagulation of the elastomer.

The particulate filler fluid may be a carbon black slurry or any othersuitable filler in a suitable carrier fluid. Selection of the carrierfluid will depend largely upon the choice of particulate filler and uponsystem parameters. Both aqueous and non-aqueous liquids may be used,with water being preferred in many embodiments in view of its cost,availability and suitability of use in the production of carbon blackand certain other filler slurries. Small amounts of water-miscibleorganic solvents may also be included in aqueous carrier fluids.

Selection of the particulate filler or mixture of particulate fillerswill depend largely upon the intended use of the elastomer masterbatchproduct. As used here, particulate filler can include any material whichis appropriate for use in the masterbatch process used to produce themasterbatch crumb. Suitable particulate fillers include, for example,conductive fillers, reinforcing fillers, fillers comprising short fibers(typically having an L/D aspect ratio less than 40), flakes, etc. Inaddition to carbon black and silica-type fillers, discussed in moredetail below, fillers can be formed of clay, glass, polymer, such asaramid fiber, etc. It is expected that any filler suitable for use inelastomer compositions may be incorporated into elastomer compositesaccording to various embodiments of the invention. Of course, blends ofthe various particulate fillers discussed herein may also be used.

When a carbon black filler is used, selection of the carbon black willdepend largely upon the intended use of the elastomer masterbatchproduct. Optionally, the carbon black filler can include also anymaterial which can be slurried and combined with a latex in theparticular wet masterbatch process selected by the skilled artisan.Exemplary particulate fillers include but are not limited to carbonblack, fumed silica, precipitated silica, coated carbon black,chemically functionalized carbon blacks, such as those having attachedorganic groups, and silicon-treated carbon black, either alone or incombination with each other. Exemplary carbon blacks include ASTM N100series-N900 series carbon blacks, for example N100 series carbon blacks,N200 series carbon blacks, N300 series carbon blacks, N700 series carbonblacks, N800 series carbon blacks, or N900 series carbon blacks.Elastomer composites containing ASTM N100, N200, and/or N300 seriesblacks and/or carbon blacks having similiarly high or higher surfaceareas, e.g, a surface area measured by the statistical thickness method(STSA), expressed as square meters per gram of carbon black, accordingto the procedure set forth in ASTM D6556 (STSA) of 68 m2/g or greater,for example, 75 m²/g or greater, or 95 m²/g or greater, for example,from 68 m²/g to 400 m²/g may especially benefit from the teachingsherein. In certain preferred embodiments, such carbon blacks have astructure, as measured by dibutyl phthalate adsorption, of at least 60mL/100 g, for example, at least 80 mL/100 g, or from 60 mL/100 g to 160mL/100 g. Carbon blacks sold under the Regal®, Black Pearls®, Spheron®,Sterling®, and Vulcan® trademarks available from Cabot Corporation, theRaven®, Statex®, Furnex®, and Neotex® trademarks and the CD and HV linesavailable from Columbian Chemicals, and the Corax®, Durax®, Ecorax®, andPurex® trademarks and the CK line available from Evonik (Degussa)Industries, and other fillers suitable for use in rubber or tireapplications, may also be exploited for use with various embodiments.Suitable chemically functionalized carbon blacks include those disclosedin International Application No. PCT/US95/16194 (WO 96/18688), thedisclosure of which is hereby incorporated by reference.

Both silicon-coated and silicon-treated carbon blacks may be employed invarious embodiments. In silicon-treated carbon black, a siliconcontaining species such as an oxide or carbide of silicon is distributedthrough at least a portion of the carbon black aggregate as an intrinsicpart of the carbon black. Conventional carbon blacks exist in the formof aggregates, with each aggregate consisting of a single phase, whichis carbon. This phase may exist in the form of a graphitic crystalliteand/or amorphous carbon, and is usually a mixture of the two forms.Carbon black aggregates may be modified by depositing silicon-containingspecies, such as silica, on at least a portion of the surface of thecarbon black aggregates. The result may be described as silicon-coatedcarbon blacks.

The materials described herein as silicon-treated carbon blacks are notcarbon black aggregates which have been coated or otherwise modified,but actually represent a different kind of aggregate having two phases.One phase is carbon, which will still be present as graphiticcrystallite and/or amorphous carbon, while the second phase is silica(and possibly other silicon-containing species). Thus, thesilicon-containing species phase of the silicon-treated carbon black isan intrinsic part of the aggregate; it is distributed throughout atleast a portion of the aggregate. A variety of silicon-treated blacksare available from Cabot Corporation under the Ecoblack™ name. It willbe appreciated that the multiphase aggregates are quite different fromthe silica-coated carbon blacks mentioned above, which consist ofpre-formed, single phase carbon black aggregates havingsilicon-containing species deposited on their surface. Such carbonblacks may be surface-treated in order to place a silica functionalityon the surface of the carbon black aggregate as described in, e.g., U.S.Pat. No. 6,929,783.

One or more additives also may be pre-mixed, if suitable, with theparticulate slurry or with the elastomer latex fluid or may be combinedwith the mixture of these during coagulation. Additives also can bemixed into the coagulating mixture. Numerous additives are well known tothose skilled in the art and include, for example, antioxidants,antiozonants, plasticizers, processing aids (e.g., liquid polymers, oilsand the like), resins, flame-retardants, extender oils, lubricants, anda mixture of any of them. Exemplary additives include but are notlimited to zinc oxide and stearic acid. The general use and selection ofsuch additives is well known to those skilled in the art. It should beunderstood that the elastomer composites disclosed here includevulcanized compositions (VR), thermoplastic vulcanizates (TPV),thermoplastic elastomers (TPE) and thermoplastic polyolefins (TPO). TPV,TPE, and TPO materials are further classified by their ability to beextruded and molded several times without loss of performancecharacteristics.

The fraction of the second elastomer with respect to the total rubber inthe composite (i.e., the amount of rubber contributed to the coagulum bythe second elastomer latex with respect to the total amount of rubber inthe coagulum) may be adjusted, e.g., by adjusting the relative flowrates of the two elastomer latices. Other variables that may bemanipulated to optimize the filler loading include the absolute flowrate of the first elastomer latex and filler slurry (e.g., theproduction rate), the relative flow rate of the first elastomer latexand filler slurry (e.g., the filler loading), the location where thesecond elastomer latex is injected, and the size of injector 42. Thefraction of the second elastomer with respect to total rubber may befrom about 0.5 wt % to about 50 wt %, for example from about 1 wt % toabout 45 wt %, from about 5 wt % to about 40 wt %, from about 10 wt % toabout 15 wt %, from about 15 wt % to about 20 wt %, from about 20 wt %to about 25 wt %, from about 25 wt % to about 30 wt %, from about 30 wt% to about 35 wt %, from about 35 wt % to about 40 wt %, or from about40 wt % to about 45 wt %. In certain embodiments, the fraction may befrom about 16 wt % to about 38 wt %. The proportion of the secondelastomer that may be used depends in part on the desired compositionbut may be physically limited depending on the amount of the firstelastomer latex that should be injected into mixing portion 10 togenerate the initial coagulating mixture.

The amount of filler in the elastomer composite may be any amount offiller that is used to make elastomer composites. For example, rubbersmay be produced with at least about 10 phr (parts per hundred of rubberby weight), at least about 20 phr, at least about 30 phr, at least about40 phr, at least about 50 phr, at least about 55 phr, at least about 60phr, at least about 65 phr at least about 70 phr, at least about 75 phr,at least about 80 phr, at least about 85 phr, at least about 90 phr, atleast about 95 phr, or at least about 100 phr of filler. However, theteachings herein will provide greater advantages with respect to otherwet masterbatch methods at higher loadings of filler, for example, fromabout 40 phr to about 100 phr, from about 50 phr to about 95 phr, fromabout 55 phr to about 90 phr, from about 60 phr to about 85 phr, fromabout 60 phr to about 80 phr, from about 65 phr to about 75 phr, or fromabout 45 phr to about 70 phr. One of skill in the art will recognizethat what constitutes a “high loading” will depend on the morphology ofthe filler, including, e.g., its surface area and structure.

In some embodiments, the use of secondary latex increases the maximumfiller loading (e.g., the maximum loading of filler while producing acoherent coagulum), by about 3% to about 30%, for example, from about 3%to about 5%, from about 5% to about 10%, from about 10% to about 15%,from about 15% to about 20%, from about 20% to about 25%, or from about25% to about 30%, with respect to the maximum loading of filler whileproducing a coherent coagulum without the use of secondary latex.

The masterbatch crumb produced from the first elastomer latex, theparticulate filler slurry, and the second elastomer latex emerges fromthe discharge end of the coagulum reactor as a substantially constantflow of coagulum concurrently with the on-going feeding of the elastomerlatices and particulate filler slurry streams into the coagulum reactor11. Preferably, the masterbatch crumb is in the form of a “coherentcoagulum,” a continuous composite in which the carbon black is dispersedwithin the coagulated latex, rather than a discontinuous flow ofcomposite in which discrete globules of coagulated latex are separatedby an aqueous carrier. Nonetheless, discontinuous coagulum may beprocessed by manual or batch dewatering methods, followed by thermaldrying. Preferably, continuous coagulum is created and then formed intoa desirable extrudate, for example, having about 70-85% water content.After formulation, the resulting masterbatch crumb may be passed tosuitable drying and compounding apparatus.

In one embodiment, the masterbatch crumb is passed from coagulum reactor11 to a de-watering extruder via a simple gravity drop or other suitableapparatus known to those of skill in the art. The dewatering extrudermay bring the elastomer composite from, e.g., approximately 70-85% watercontent, to a desired water content, e.g., approximately 1% to 20% watercontent. The optimal water content may vary with the elastomer employed,the type of filler, and the desired downstream processing procedure.Suitable de-watering extruders are well known and commercially availablefrom, for example, the French Oil Mill Machinery Co. (Piqua, Ohio, USA).

After de-watering, the resulting dewatered coagulum may be dried. Incertain embodiments, the dewatered coagulum is simply thermally dried.Preferably, the dewatered coagulum emerging from the de-wateringextruder is mechanically masticated while drying. For example, thedewatered coagulum may be mechanically worked with one or more of acontinuous mixer, an internal mixer, a twin screw extruder, a singlescrew extruder, or a roll mill. Suitable masticating devices are wellknown and commercially available, including for example, a UnimixContinuous Mixer and MVX (Mixing, Venting, eXtruding) Machine fromFarrel Corporation of Ansonia, Conn., a long continuous mixer fromPomini, Inc., a Pomini Continuous Mixer, twin rotor corotatingintermeshing extruders, twin rotor counterrotating non-intermeshingextruders, Banbury mixers, Brabender mixers, intermeshing-type internalmixers, kneading-type internal mixers, continuous compounding extruders,the biaxial milling extruder produced by Kobe Steel, Ltd., and a KobeContinuous Mixer. Alternative masticating apparatus suitable for usewith various embodiments of the invention will be familiar to those ofskill in the art. Exemplary methods for mechanically masticatingdewatered composite are disclosed in U.S. Pat. Nos. 6,929,783 and6,841,606, and PCT Application No. US09/000732, the contents of all ofwhich are incorporated herein by reference.

In certain embodiments, additives can be combined with the dewateredcoagulum in the mechanical mixer. Specifically, additives such as filler(which may be the same as, or different from, the filler used in thecoagulum reactor; exemplary fillers include silica and zinc oxide, withzinc oxide also acting as a curing agent), other elastomers, other oradditional masterbatch, antioxidants, antiozonants, plasticizers,processing aids (e.g., stearic acid, which can also be used as a curingagent, liquid polymers, oils, waxes, and the like), resins,flame-retardants, extender oils, lubricants, and a mixture of any ofthem, can be added in the mechanical mixer. In certain otherembodiments, additional elastomers can be combined with the dewateredcoagulum to produce elastomer blends. Exemplary elastomers include, butare not limited to, rubbers, polymers (e.g., homopolymers, copolymersand/or terpolymers) of 1,3-butadiene, styrene, isoprene, isobutylene,2,3-dialkyl-1,3-butadiene, where alkyl may be methyl, ethyl, propyl,etc., acrylonitrile, ethylene, and propylene and the like. Methods ofproducing masterbatch blends are disclosed in our commonly owned U.S.Pat. Nos. 7,105,595, 6,365,663, and 6,075,084. Alternatively or inaddition, traditional compounding techniques may be used to combinevulcanization agents and other additives known in the art with thedewatered coagulum or, where a masticating apparatus is used to dry thematerial, the resulting masticated masterbatch, depending on the desireduse.

The invention also concerns the use of resulting elastomer compositeblend accordingly to any of the mentioned embodiments for thefabrication of tires, in particular for the compositions of tire treads,carcass, tire sidewalls, wire-skim for tires, and cushion gum forretread tires.

The rubber compositions of the invention also comprise all or a portionof the usual additives generally used in the elastomer compositionsintended for the manufacture of tires, such as, for example, protectionagents, such as antiozone waxes, chemical antiozonants, antioxidants,reinforcing resins, methylene acceptors (for example phenolic novolakresin) or methylene donors (for example HMT or H3M), a crosslinkingsystem based either on sulphur or on donors of sulphur and/or peroxideand/or bismaleimides, vulcanization accelerators, or vulcanizationactivators.

These compositions can also comprise coupling activators when a couplingagent is used, agents for covering the inorganic filler or moregenerally processing aids capable, in a known way, by virtue of animprovement in the dispersion of the filler in the rubber matrix and ofa lowering of the viscosity of the compositions, of improving theirproperty of processing in the raw state; these agents are, for example,hydrolysable silanes, such as alkylalkoxysilanes, polyols, polyethers,amines, or hydroxylated or hydrolysable polyorganosiloxanes.

The rubber compositions of the invention are manufactured in appropriatemixers using two successive preparation phases according to a generalprocedure well known to a person skilled in the art: a first phase ofthermomechanical working or kneading (sometimes described as“non-productive” phase) at high temperature, up to a maximum temperatureof between 130° C. and 200° C., preferably between 145° C. and 185° C.,followed by a second phase of mechanical working (sometimes described as“productive” phase) at a lower temperature, typically of less than 120°C., for example between 60° C. and 100° C., finishing phase during whichthe crosslinking or vulcanization system is incorporated.

The crosslinking system proper is preferably based on sulphur and on aprimary vulcanization accelerator, in particular on an accelerator ofsulphenamide type. Added to this vulcanization system are various knownsecondary accelerators or vulcanization activators, such as zinc oxide,stearic acid, guanidine derivatives (in particular diphenylguanidine),and the like, incorporated during the first non-productive phase and/orduring the productive phase. The level of sulphur is preferably between0.5 and 12 phr, preferably between 1 and 10 phr, and that of the primaryaccelerator is preferably between 0.5 and 5.0 phr.

Use may be made, as accelerator (primary or secondary) of any compoundcapable of acting as accelerator of the vulcanization of dieneelastomers in the presence of sulphur, in particular accelerators of thethiazoles type and their derivatives, accelerators of thiurams types, orzinc dithiocarbamates. These accelerators are more preferably chosenfrom the group consisting of 2-mercaptobenzothiazyl disulphide(abbreviated to “MBTS”), N-cyclohexyl-2-benzothiazolesulphenamide(abbreviated to “CBS”), N,N-dicyclohexyl-2-benzothiazolesulphenamide(“DCBS”), N-tert-butyl-2-benzothiazolesulphenamide (“TBBS”),N-tert-butyl-2-benzothiazolesulphenimide (“TBSI”), zincdibenzyldithiocarbamate (“ZBEC”) and the mixtures of these compounds.

The final composition thus obtained is subsequently calendered, forexample in the form of a sheet or of a plaque, in particular forlaboratory characterization, or else extruded in the form of a rubberprofiled element which can be used directly like for example tire tread.

The vulcanization (or curing) is carried out in a known way at atemperature generally of between 130° C. and 200° C. for a sufficienttime which can vary, for example, between 5 and 90 min depending inparticular on the curing temperature, the vulcanization system adoptedand the vulcanization kinetics of the composition under consideration.

The invention relates to the rubber compositions and to the treadsdescribed above, both in the raw state (i.e., before curing) and in thecured state (i.e., after crosslinking or vulcanization).

The present invention will be further clarified by the followingexamples which are intended to be only exemplary in nature

EXAMPLES Example 1 Carbon Black Slurry Preparation

Dry carbon black (grade indicated in Table 1, below, obtained from CabotCorporation) was mixed with water and ground to form a slurry having aconcentration of about 10-15 wt %. The slurry was fed to a homogenizerat an operating pressure of around 3000 psig to produce a finelydispersed carbon black slurry, and the slurry was introduced as a jetinto the mixing zone. The carbon black flow rate was adjusted to about690-960 kg/hr (wet basis) to modify final carbon black loading levels incomposites produced with field latex and to about 1145 kg/hr (wet basis)when latex concentrate was employed.

TABLE 1 DBP adsorption** Carbon Black Grade STSA* (mg/g) (mL/100 g) N234114 125 N134 131 127 Experimental Black 1 154 123 *ASTM D6556 **ASTMD2414

Primary Latex Delivery

Natural rubber materials described in Table 2 (field latex unlessindicated otherwise in Table 2) were pumped to the mixing zone of thecoagulum reactor. The latex flow rate was adjusted between about 320-790kg/h (wet basis) in order to modify final carbon black loading levels.

Carbon Black and Latex Mixing

The carbon black slurry and latex were mixed by entraining the latexinto the carbon black slurry in a mixing portion (e.g., mixing portion10) of a coagulum reactor similar to that shown in FIG. 1. During theentrainment process, the carbon black was intimately mixed into thelatex and the mixture coagulated.

Secondary Latex Delivery

Natural rubber latex materials described in Table 2 were pumped intovarious locations downstream of the mixing portion of the coagulumreactor at a pressure of 3-8 bar starting at a rate of about 80 kg/hour(wet basis). The latex was injected at a right angle to the wall of thecoagulum reactor to which the injection line (e.g., element 28) isaffixed. The pumping rate was gradually increased to at most 300 kg/hr(wet basis) until the coagulum emerging from the diffuser exhibited thedesired morphology. Downstream of the mixing portion, a diffuser portionhad a series of sections, each one having progressively higher diameterthan the previous section, with a beveled transition portion in betweensections. The first section of the diffuser (e.g., 18 a in FIG. 1) was 4inches (10.2 cm) long; the second section (e.g., 18 b in FIG. 1) was 3inches (7.6 cm) long. The angle of the transition region (e.g. a in FIG.2) was 7 degrees. The ratio of the diameters of the second section(e.g., 18 b in FIG. 1) to the first section (e.g., 18 a in FIG. 1), wasabout 1.7. The location into which the secondary latex was pumped andthe fraction of the rubber from the secondary latex in the final product(i.e., the ratio of rubber from the secondary latex with respect to thetotal rubber from the primary and secondary latex streams) are indicatedin Table 2 below. Data shown in bold face reflect the maximum loadingachieved for a particular location of secondary latex injection, listedin Table 3 below.

TABLE 2 CB grade Secondary latex injection N234 N234 N234 locationcontrol Middle of first section Middle of second section Calculated CBloading after 56 62 70 75 80 85 90 95 1^(st) latex, phr Prod. Rate*.Kg/hr 262 255 247 232 227 211 208 203 1^(st) latex DRC**, % 30.7 30.730.7 30.7 30.7 30.7 30.7 30.7 2^(nd) latex DRC, % — 30.7 30.7 30.7 30.730.7 30.7 30.7 2^(nd) latex DRC/total DRC, % — 31 33 35 36 38 39 40Residence time before 2^(nd) 1.2 1.2 1.3 1.3 6.5 6.5 6.7 latex addition(10⁻² s) Coherent coagulum Yes, Yes Yes Yes Yes Yes No No sometimesdiscontinuous Measured CB loading, phr 59.7 49.4 54.7 58.4 59.2 62.564.2 68.3 *Based on carbon black and first latex only **Dry RubberContent CB grade N234 N234 N234 N234 middle of middle of 1″ upstream 1″downstream Secondary latex injection first second from the middle fromthe middle location section section of 2^(nd) section of 1^(st) sectionCalculated CB loading after 1^(st) 67 67 70 69 63 70 72 latex, phr Prod.Rate*. Kg/hr 253 250 238 237 253 243 237 1^(st) latex DRC**, % 30.7 30.730.7 30.7 30.7 30.7 30.7 2^(nd) latex DRC***, % 14.1 14.1 14.2 14.2 14.014.8 14.8 2^(nd) latex DRC/total DRC, % 18 11 12 12 11 19 20 Residencetime before 2^(nd) latex 1.2 5.8 4.4 4.5 1.8 1.8 1.9 addition (10⁻² s)Coherent coagulum Yes Yes No Yes Yes Yes Yes Measured CB loading, phr59.9 62.1 67 65 62.2 62.5 62.3 *Based on carbon black and first latexonly **Dry Rubber Content ***DRC adjusted by dilution with water CBgrade N234 N234 Secondary latex injection transition between first andN234 transition between first and location second sections controlsecond sections Calculated CB loading after 1^(st) 77 79 78 60 87 83 85latex, phr Prod. Rate*. Kg/hr 233 217 217 266 205 221 215 1^(st) latexDRC**, % 30.7 30.7 30.7 28.7 28.7 28.7 28.7 2^(nd) latex DRC***, % 13.613.6 16.0 15.1 15.1 15.1 2^(nd) latex DRC/total DRC, % 23 25 28 24 22 23Residence time before 2^(nd) 2.6 2.8 2.8 2.8 2.7 2.7 latex addition(10⁻² s) Coherent coagulum Yes No Yes No Yes Yes Yes Measured CBloading, phr 69.8 71.5 71.1 59.7 70.2 67.9 68.8 *Based on carbon blackand first latex only **Dry Rubber Content ***DRC adjusted by dilutionwith water CB grade Secondary latex injection N234 location transitionbetween first and second sections Calculated CB loading after 1^(st) 7880 82 83 80 latex, phr Prod. Rate*. Kg/hr 222 221 218 215 214 1^(st)latex DRC**, % 28.7 28.7 28.7 28.7 28.7 2^(nd) latex DRC***, % 14.8 14.814.8 14.8 10.7 2^(nd) latex DRC/total DRC, % 21 22 22 22 17 Residencetime before 2^(nd) latex 2.6 2.7 2.7 2.7 2.7 addition (10⁻² s) Coherentcoagulum Yes Yes Yes Yes Yes Measured CB loading, phr 62.6 66.1 65.966.9 66.4 *Based on carbon black and first latex only **Dry RubberContent ***DRC adjusted by dilution with water CB grade ExperimentalBlack 1 1″ upstream Secondary latex from middle injection locationControl of 2nd section transition between first and second sectionsCalculated CB loading 49 42 57 52 59 70 55 62 62 79 82 after 1st latex,phr Prod. Rate*. kg/hr 272 295 244 323 240 211 243 229 230 199 207 1stlatex DRC**, % 28.7 29.6 29.6 29.6 29.6 29.6 29.6 29.6 29.6 29.6 29.62nd latex DRC***, % — — 10.7 10.7 10.7 10.7 10.7 27.0 27.0 27.0 29.6 2ndlatex DRC/total — — DRC, % 14 10 14 16 9 21 21 36 38 Residence timebefore 4.0 3.1 2.4 2.6 2.4 2.4 2.4 2.7 2.6 2^(nd) latex addition (10⁻²s) Coherent coagulum No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes MeasuredCB loading, 46.3 49.3 51.4 48.4 51.6 54.3 51.3 51.7 51.4 55 54.9 phr*Based on carbon black and first latex only **Dry Rubber Content ***DRCadjusted by dilution with water CB grade Experimental Black 1 N134 N234Secondary latex injection transition between first and transitionbetween first and location second sections Control second sectionsCalculated CB loading after 80 84 87 90 60 83 83 87 65 1st latex, phrProd. Rate*. kg/hr 286 288 292 302 280 296 303 279 496 1st latex DRC**,% 30.3 30.3 30.3 30.3 29.8 29.8 29.8 29.8 59.3*** 2nd latex DRC, % 30.330.3 30.3 30.3 — 29.8 29.8 29.8 59.3*** 2nd latex DRC/total DRC, % 22 2727 30 — 17 20 25 27 Residence time before 2^(nd) 2.4 2.4 2.4 2.3 — 2.32.3 2.5 1.9 latex addition (10⁻² s) Coherent Coagulum Yes Yes Yes YesYes Yes Yes Yes Yes Measured (actual) CB 60.3 60.1 59 61.6 54.9 63.562.6 64.4 47.8 loading, phr *Based on carbon black and first latex only**Dry Rubber Content ***Latex Concentrate

For successful examples incorporating secondary latex according to anembodiment of the invention, a masterbatch crumb exited the coagulumreactor as a continuous flow of coherent coagulum. Unsuccessful examplesemploying secondary latex may be contrasted with successful sampleshaving similar operating conditions; in general, rubber recovered fromsuch examples contained higher loadings of carbon black. Such samplesemerged from the coagulum reactor as a discontinuous, sandy coagulumthat caused the dewatering extruder to back up. Table 3, below, showsthe maximum loading, i.e., the maximum filler content in the elastomercomposite, in parts per hundred of rubber (phr), for which coherentcoagulum was produced (that is, attempts to produce masterbatch crumbwith higher filler content did not result in a coherent coagulum).

TABLE 3 Maximum Carbon Black Loading, phr Injection point inExperimental diffuser N234 N134 Black 1 Control (no 59.7* 54.9 49.3injection) Middle of first 59.9 — — section 1″ downstream from 62.5 — —middle of first section Transition between 71.1 64.4 61.6 first andsecond section 1″ upstream from 65 — 51.4 middle of the second sectionMiddle of second 62.1 — — section *coagulum intermittently discontinuous

The results show that operating variables such as the flow rate of theprimary and secondary latex streams, the production rate, the proportionof secondary rubber, and the carbon black loading may be optimized withrespect to one another to improve processability and increase fillerloading. FIG. 3 shows the highest loadings achieved with and withoutsecondary latex for the three grades of carbon black described above.The results show that while the morphology of the carbon blackinfluences the maximum loading that can be achieved while producingcoherent coagulum, the use of secondary latex provides a clear andconsistent improvement in the achievable loading.

Dewatering

The masterbatch crumb discharged from the coagulum reactor was dewateredto 10-20% moisture with a dewatering extruder (The French Oil MachineryCompany). In the extruder, the masterbatch crumb was compressed, andwater squeezed from the crumb was ejected through a slotted barrel ofthe extruder.

Drying and Cooling

The dewatered coagulum was dropped into a continuous compounder (FarrelContinuous Mixer (FCM), Farrel Corporation) where it was masticated andmixed with 1 phr of antioxidant(N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD, Flexsys, St.Louis, Mo.). The moisture content of the masticated masterbatch exitingthe FCM was around 1-2%. The masticated masterbatch was furthermasticated and cooled on an open mill to form a dried elastomercomposite. The actual carbon black loading levels were determined bynitrogen pyrolysis (values listed on Tables 2A-2E) or TGA (values listedon Table 2F) on dried product. The dried elastomer composite wasvulcanized; the mechanical properties of the vulcanized elastomercomposite (e.g., tan delta, ratio of stresses at 300% and 100% strain)exhibited a variation with loading similar to that of vulcanizedelastomer composites having lower filler loadings and prepared using thesame techniques but without secondary latex. The use of secondary latexinjection enables the manufacture of more highly loaded elastomercomposites without sacrificing performance of the final rubbercompounds.

Example 2 Filler Slurry Preparation

Silicon-treated carbon black (CRX™ 2000 ECOBLACK® silicon-treated carbonblack, available from Cabot Corporation) is mixed with water and groundto form a slurry having a concentration of about 10-15 wt %. The slurryis fed to a homogenizer at an operating pressure of around 3000 psig toproduce a finely dispersed carbon black slurry, and the slurry isintroduced as a jet into the mixing zone. The slurry flow rate isadjusted to about 690-960 kg/hr (wet basis) to modify final fillerloading levels in composites produced with field latex and to about 1145kg/hr (wet basis) when latex concentrate is employed.

Primary Latex Delivery

Either field latex having a dry rubber content of about 27-31% ornatural rubber latex concentrate is pumped to the mixing zone of thecoagulum reactor. The latex flow rate is adjusted between about 320-790kg/h (wet basis) in order to modify final filler loading levels.

Filler and Latex Mixing

The filler slurry and latex are mixed by entraining the latex into thefiller slurry in a mixing portion (e.g., mixing portion 10) of acoagulum reactor similar to that shown in FIG. 1. During the entrainmentprocess, the filler is intimately mixed into the latex and the mixturecoagulates. Downstream of the mixing portion, a diffuser portion has aseries of sections, each one having progressively higher diameter thanthe previous section, with a beveled transition portion in betweensections.

Secondary Latex Delivery

Field latex is pumped into the coagulating mixture of filler slurry andlatex at the transition between the first and second sections (e.g., 20a in FIG. 1) at a pressure of 3-8 bar starting at a rate of about 80kg/hour (wet basis). The latex is injected at a right angle to the wallof the coagulum reactor. The pumping rate is gradually increased to atmost 300 kg/hr (wet basis) until the coagulum emerging from the diffuserexhibits the desired morphology.

Dewatering

The masterbatch crumb discharged from the coagulum reactor is dewateredto 10-20% moisture with a dewatering extruder (The French Oil MachineryCompany). In the extruder, the masterbatch crumb is compressed, andwater squeezed from the crumb is ejected through a slotted barrel of theextruder.

Drying and Cooling

The dewatered coagulum is dropped into a continuous compounder (FarrelContinuous Mixer (FCM), Farrel Corporation) where it is masticated andmixed with 1 phr of antioxidant(N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD, Flex sys, St.Louis, Mo.) and 1.5 phr of a coupling agent(bis-(triethoxysilylpropyl)tetrasulfide (TESPT, Si-69, available fromEvonik Industries, Essen, Germany)). The moisture content of themasticated masterbatch exiting the FCM is around 1-2%. The product isfurther masticated and cooled on an open mill.

Example 3 Filler Slurry Preparation

A mixture of carbon black and silica (N234 carbon black, available fromCabot Corporation, and HiSil® 233 silica, available from PPG Industries,Pittsburgh, Pa.) is mixed with water and ground to form a slurry havinga concentration of about 10-15 wt %, in which the ratio of carbon blackto silica ranges from 60:40 to 80:20 by mass. The slurry is fed to ahomogenizer at an operating pressure of around 3000 psig to produce afinely dispersed carbon black slurry, and the slurry is introduced as ajet into the mixing zone. The slurry flow rate is adjusted to about690-960 kg/hr (wet basis) to modify final filler loading levels incomposites produced with field latex and to about 1145 kg/hr (wet basis)when latex concentrate is employed.

Primary Latex Delivery

Either field latex having a dry rubber content of about 27-31% ornatural rubber latex concentrate is pumped to the mixing zone of thecoagulum reactor. The latex flow rate is adjusted between about 320-790kg/h in order to modify final filler loading levels.

Filler and Latex Mixing

The filler slurry and latex are mixed by entraining the latex into thefiller slurry in a mixing portion (e.g., mixing portion 10) of acoagulum reactor similar to that shown in FIG. 1. During the entrainmentprocess, the filler is intimately mixed into the latex and the mixturecoagulates.

Secondary Latex Delivery

Field latex is pumped into the coagulating mixture of filler slurry andlatex at the transition between the first and second sections (e.g., 20a in FIG. 1) at a pressure of 3-8 bar starting at a rate of about 80kg/hour (wet basis). The latex is injected at a right angle to the wallof the coagulum reactor. The pumping rate is gradually increased to atmost 300 kg/hr (wet basis) until the coagulum emerging from the diffuserexhibits the desired morphology.

Dewatering

The masterbatch crumb discharged from the coagulum reactor is dewateredto 10-20% moisture with a dewatering extruder (The French Oil MachineryCompany). In the extruder, the masterbatch crumb is compressed, andwater squeezed from the crumb is ejected through a slotted barrel of theextruder.

Drying and Cooling

The dewatered coagulum is dropped into a continuous compounder (FarrelContinuous Mixer (FCM), Farrel Corporation) where it is masticated andmixed with 1 phr of antioxidant(N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD, Flexsys, St.Louis, Mo.) and 1.5 phr of a coupling agent(bis-(triethoxysilylpropyl)tetrasulfide (TESPT, Si-69, available fromEvonik Industries, Essen, Germany)). The moisture content of themasticated masterbatch exiting the FCM is around 1-2%. The product isfurther masticated and cooled on an open mill to form a dried elastomercomposite.

Example 4

Dry carbon black (N234, obtained from Cabot Corporation) was mixed withwater and ground to form a slurry having a concentration of about 10-15wt %. The slurry was fed to a homogenizer at an operating pressure ofaround 3000 psig to produce a finely dispersed carbon black slurry, andthe slurry was introduced as a jet into the mixing zone. The carbonblack flow rate (dry basis) is specified in Table 4, below.

Primary Latex Delivery

Field latex having a dry rubber content of about 27-31% was pumped tothe mixing zone of the coagulum reactor. The delivery rate of primaryrubber (dry rubber basis) into the mixing zone is listed in Table 4,below.

Carbon Black and Latex Mixing

The carbon black slurry and latex were mixed by entraining the latexinto the carbon black slurry in a mixing portion (e.g., mixing portion10) of a coagulum reactor similar to that shown in FIG. 1. During theentrainment process, the carbon black was intimately mixed into thelatex and the mixture coagulated.

Secondary Latex Delivery

Field latex was pumped into the downstream, diffuser portion of thecoagulum reactor at the transition between the first and second sectionsof the diffuser (e.g., 20 a on FIG. 1), and the angle α (see FIG. 2) was7 degrees. The length of the first section of the diffuser (e.g., 18 ain FIG. 1) was varied between 4 and 8.5 inches; the resulting residencetime before introduction of the secondary latex stream is listed inTable 4, along with the delivery rate of secondary rubber (dry rubberbasis). The corresponding residence time for the Comparative Example(i.e., the residence time in the first section of the diffuser) was1.8*10⁻² s. The pumping rates of the primary and secondary latex and ofthe carbon black slurry were adjusted to achieve a production rate of450-500 kg/hr (dry basis).

TABLE 4 Comparative Example Example 4-1 4-2 4-3 4-4 4-5 4-6 Carbon blackflow rate 153 167 197 192 197 195 195 (kg/hr, dry basis) Primary rubberflow rate 222 189 209 194 221 186 259 (kg/hr, dry rubber basis)Secondary rubber flow 0 64 61 66 67 92 42 rate (kg/hr, dry rubber basis)Residence time before 2^(o) — 1.8 1.9 2.4 3.0 2.4 2.2 elastomer (10⁻² s)2⁰ elastomer/total 0 25.2 22.5 25.4 23.3 33.3 13.9 elastomer (%)Measured CB loading 64.5 64.4 65.3 68 64.4 65.6 63.2 (phr)

Results from Examples 4-1 through 4-4 are shown in FIG. 4. FIG. 4clearly shows an optimum residence time for maximizing filler loading.Such a maximum is consistent with the theory described above. Accordingto the theory, introduction of the secondary latex stream beforesubstantial decoration of the latex particles causes the rubberparticles in the secondary latex stream to also become decorated, ratherthan binding rubber-filler aggregates together, while the secondarylatex stream is not completely mixed with the coagulating mixture if itis introduced too far downstream. In Examples 4-5 and 4-6, the injectionrate of the secondary rubber flow was varied while maintaining aresidence time similar to that of Example 4-3. The results areconsistent with the theory described above; only a certain amount ofsecondary latex is required to bind together the discrete rubber-filleraggregates into a coherent coagulum, and additional secondary latex onlydilutes the final product loading.

Dewatering

The masterbatch crumb discharged from the coagulum reactor was dewateredto 10-20% moisture with a dewatering extruder (The French Oil MachineryCompany). In the extruder, the masterbatch crumb was compressed, andwater squeezed from the crumb was ejected through a slotted barrel ofthe extruder.

Drying and Cooling

The dewatered coagulum was dropped into a continuous compounder (FarrelContinuous Mixer (FCM), Farrel Corporation) where it was masticated andmixed with 1 phr of antioxidant(N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD, Flexsys, St.Louis, Mo.). The moisture content of the masticated masterbatch exitingthe FCM was around 1-2%. The product was further masticated and cooledon an open mill to form a dried elastomer composite. The actual carbonblack loading levels were determined by TGA on the dried elastomercomposite and are listed in Table 4. The dried elastomer composite wasvulcanized; the mechanical properties of the vulcanized elastomercomposite (e.g., tan delta, ratio of stresses at 300% and 100% strain)exhibited a variation with loading similar to that of vulcanizedelastomer composites having lower filler loadings and prepared using thesame techniques but without secondary latex. The use of secondary latexinjection enables the manufacturing of more highly loaded elastomercomposites without sacrificing performance of the final rubbercompounds.

Example 5

This example shows the improvements of rubber composition propertiesincluding elastomer composite with high volume fraction of carbon blackprepared according to the invention, compared to the already improvedproperties of tire comprising rubber composition based on elastomercomposite having lesser volume fraction of carbon black prepared by thewet mix method used in Example 4 to prepare control samples and tovulcanized rubber compositions prepared by dry mixing.

Preparation of Masterbaches

Masterbaches A were prepared according to Example 1, as follows:

-   -   Masterbatch A1 corresponds to N234, measured CB loading of 66.1        phr, of table 2D,    -   Masterbatch A2 corresponds to Experimental Black 1, measured CB        loading of 59 phr, of table 2F,    -   Masterbatch A3 corresponds to N134, measured CB loading of 64.4        phr, of table 2F

Masterbatches B were prepared with the same carbon black and the samefield latex according to the wet mix method used in Example 4 to preparecontrol samples, as follows:

-   -   Masterbatch B1 includes 50 phr of N234,    -   Masterbatch B2 includes 49 phr of Experimental Black 1,    -   Masterbatch B3 includes 50 phr of N134,

Preparation of Rubber Compositions

The tests which follow are carried out in the following way: the dieneelastomer and the reinforcing filler or the masterbatches includingdiene elastomers and reinforcing fillers were introduced into aninternal mixer, 70% filled and having an initial vessel temperature ofapproximately 50° C., followed, after kneading for one minute, by thevarious other ingredients, with the exception of the sulphur andsulphenamide primary accelerator. Thermomechanical working(non-productive phase) was then carried out in one or two stages (totalduration of the kneading equal to approximately 5 min), until a maximum“dropping” temperature of approximately 165° C. is reached.

The mixture thus obtained was recovered and cooled and then sulphur andsulphenamide accelerator were added on an external mixer (homofinisher)at 30° C., the combined mixture was mixed (productive phase) for 3 to 4minutes.

The compositions were subsequently either calendered in the form ofplaques (thickness of 2 to 3 mm), for the measurement of their physicalor mechanical properties.

Rubber Compositions

Rubber compositions CA1 to CA3 and CB1 to CB3 were produced withmasterbatches A1 to A3 and B1 to B3, respectively. Comparative rubbercompositions CD1 to CD3 and CE1 to CE3 were fabricated using a drymixing process from the same carbon blacks in dry form and solid naturalrubber.

Thus all the compositions included 100 phr of natural rubber (whetherintroduced in the form of a masterbatch, or in a solid form) anddifferent grades of carbon black as shown in the following Table 5.

TABLE 5 Composition CD1 CB1 CE1 CA1 CD2 CB2 CE2 CA2 CD3 CB3 CE3 CA3 N234(phr) 50 50 66 66.1 — — — — — — — — Experimental — — — — 49 49 59 59 — —— — Black 1 (phr) N134 (phr) — — — — — — — — 50 50 64 64.4

All these compositions also included the additional ingredients shown inTable 6.

TABLE 6 Ingredients Quantity (phr) 6 PPD 2.0 Stearic Acid 2.5 ZnO 3.0CBS* (accelerator) 1.2 Sulfur 1.2*N-Cyclohexyl-2-benzothiazolesulphenamide (Flexsys: “Santocure” CBS)

Characterization of the Rubber Compositions

The diene rubber compositions were characterized, before and aftercuring, as indicated below.

1. Mooney Plasticity

Use was made of an oscillating consistometer as described in FrenchStandard NF T 43-005 (1991). The Mooney plasticity measurement wascarried out according to the following principle: the composition in theraw state (i.e., before curing) was moulded in a cylindrical chamberheated to 100° C. After preheating for one minute, the rotor rotatedwithin the test specimen at 2 revolutions/minute and the working torquefor maintaining this movement was measured after rotating for 4 minutes.The Mooney plasticity (ML 1+4) is expressed in “Mooney unit” (MU, with 1MU=0.83 newton·metre).

2 Dispersion

In a known way, filler dispersion in rubber matrix can be represented byZ value, which was measured, after reticulation, according to the methoddescribed by S. Otto and A1 in Kautschuk Gummi Kunststoffe, 58 Jahrgang,NR 7-8/2005, article titled “New Reference value for the description ofFiller Dispersion with the Dispergrader 1000NT” according to standardISO 11345.

The calculation of Z value is based on the percentage of undispersedarea, as measured by the apparatus “disperGRADER+” provided with itsprocedure and its operating software “disperDATA” by the Dynisco companyaccording to the equation:

Z=100−(percentage of undispersed area)/0.35

The percentage of undispersed area was measured using a camera with alight source at an angle of 30° with respect to the observation surface.Light dots are associated with filler and agglomerates, while the darkbackground is associated the rubber matrix; numerical treatmenttransforms the image into a black and white image, and allows thedetermination of the percentage of undispersed area, as described by S.Otto in the above mentioned document.

The higher the value Z, the better the dispersion of the filler in therubber matrix (a Z value of 100 corresponding to perfect mix and a Zvalue of 0 to poorer mix)

3 Rheometry

The measurements were carried out at 150° C. with an oscillating discrheometer, according to Standard DIN 53529-part 3 (June 1983). Thechange in the rheometric torque as a function of time describes thechange in the stiffening of the composition as a result of thevulcanization reaction. The measurements are processed according toStandard DIN 53529-part 2 (March 1983): “ti” is the induction period,that is to say the time necessary for the start of the vulcanizationreaction; tα (for example t90) is the time necessary to achieve aconversion of α %, that is to say α % (for example 90%) of thedifference between the minimum and maximum torques. The conversion rateconstant, denoted K (expressed in min⁻¹), which is first order,calculated between 30% and 80% conversion, which makes it possible toassess the vulcanization kinetics, was also measured.

4. Tensile Tests

These tensile tests make it possible to determine the elasticitystresses and the properties at break. Unless otherwise indicated, theywere carried out in accordance with French Standard NF T 46-002 ofSeptember 1988. The nominal secant moduli (or apparent stresses, in MPa)were measured in second elongation (i.e., after a cycle of accommodationto the degree of extension expected for the measurement itself) at 10%elongation (denoted M10), 100% elongation (denoted M100) and 300%elongation (denoted M300).

The properties measured before and after curing at 150° C. for 40minutes are given in the Tables 7, 8 and 9 (each table corresponding toone specific carbon black grade).

TABLE 7 Composition (with N234): CD1 CB1 Improvement (%) CE1 CA1Improvement (%) Properties before curing Mooney (MU) 45 38 15 67 46 31Curing Properties T₉₉ (min) 55 48 13 54 43 20 K (min⁻¹) 0.11 0.14 270.11 0.15 36 Properties after curing: Z value 60 84 40 68 96 41 M300(MPa) 2.92 3.22 10 4.27 4.89 14 M300/M100 1.25 1.41 13 1.21 1.46 21

TABLE 8 Composition: Improvement (with Experimental Black 1) CD2 CB2 (%)CE2 CA2 Improvement (%) Properties before curing Mooney (MU) 52 43 17 6046 23 Curing Properties T₉₉ (min) 59 52 17 60 45 25 K (min⁻¹) 0.10 0.1220 0.10 0.14 40 Properties after curing: Z value 57 77 35 53 86 62 M300(MPa) 2.96 3.33 12 3.48 4.04 16 M300/M100 1.29 1.52 18 1.27 1.52 20

TABLE 9 Composition: (with N134) CD3 CB3 Improvement (%) CE3 CA3Improvement (%) Properties before curing Mooney (MU) 47 37 21 69 46 33Curing Properties T⁹⁹ (min) 55 47 14 55 45 18 K (min⁻¹) 0.11 0.14 270.10 0.14 40 Properties after curing: Z value 65 81 25 58 95 64 M300(MPa) 2.91 2.57 12 4.19 4.97 19 M300/M100 1.30 1.21 7 1.26 1.54 22

It can be seen that all compositions prepared by a wet mix method (CA1to CA3 and CB1 to CB3), when compared with a composition having the sameingredients but prepared by dry mix method (CD1 to CD3 and CE1 to CE3),exhibited an improvement of all the properties mentioned above:dispersion (shown by Z value), processability (Mooney), rheometry (T₉₉and K) and reinforcement (M300 and M300/M100). Thus, higher loading ofcarbon black enabled by the processes of the invention preserves theimprovements obtained by a wet mix, mechanical coagulation method of thetype described in U.S. Pat. No. 6,048,923.

Moreover, when comparing compounds prepared by a wet mix method to thoseprepared by a dry mix method, the percent of improvement obtained athigh loadings of carbon black is, for all the properties discussedabove, higher that what was obtained at lower loadings of carbon black.

The foregoing description of preferred embodiments of the presentinvention has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed. Modifications and variationsare possible in light of the above teachings, or may be acquired frompractice of the invention. The embodiments were chosen and described inorder to explain the principles of the invention and its practicalapplication to enable one skilled in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto, and theirequivalents.

1. A process for manufacturing a rubber composition for tire, comprisingthe steps of: a) manufacturing a coagulated latex composite by themethod comprising a1) flowing a coagulating mixture of a first elastomerlatex comprising a first elastomer and a particulate filler slurry alonga conduit, wherein the particulate filler comprises a carbon blackhaving a dibutyl phthalate adsorption greater than 60 mL/100 g, andwherein the carbon black has a surface area and is present in thecoagulated latex composite in an amount satisfying L≧−0.26*S+94, where Lis the amount of the carbon black in the coagulated latex composite inparts per hundred of rubber (phr) and S is the surface area in m²/g asmeasured by STSA; and a2) introducing a second elastomer latexcomprising a second elastomer into the flow of the coagulating mixtureto obtain a coagulated latex composite in a form of coherent coagulumand the second elastomer latex is not decorated with filler particlesprior to the introduction step; b) dewatering the coagulated latexcomposite obtained in step a) into a desired water content; c)incorporating all the constituents of the composition for tire,including the dewatered coagulated latex composite obtained in step b),in a mixer by thermomechanically kneading the whole mixture at hightemperature, up to a maximum temperature of between 130° C. and 200° C.,then d) performing mechanical working of the resulting mixture, withincorporation of a crosslinking system, at a temperature of less than120° C.
 2. The process according to claim 1, comprising, before flowingthe coagulating mixture, generating the coagulating mixture by feeding acontinuous flow of the first elastomer latex to a mixing zone of acoagulum reactor defining an elongate coagulum zone extending from themixing zone to a discharge end and comprising the conduit, and feeding acontinuous flow of a fluid comprising a particulate filler underpressure to the mixing zone of the coagulum reactor to form thecoagulating mixture.
 3. The process according to claim 2, wherein thecontinuous flow of the fluid comprising particulate filler has avelocity from about 30 m/s to about 250 m/s, the continuous flow of thefirst elastomer latex has a velocity of at most about 10 m/s, and aresidence time of the coagulating mixture in the coagulum reactor beforeintroducing the second elastomer latex is from 1×10⁻² s to about 6×10⁻²s.
 4. The process according to claim 1, wherein the conduit comprises afirst conduit portion having a first diameter, a second conduit portionhaving a second diameter greater than the first diameter, and atransition zone therebetween having a diameter that increases from thefirst diameter to the second diameter, wherein flowing comprises flowingthe coagulating mixture into the second conduit portion from the firstconduit portion, and wherein introducing comprises introducing thesecond elastomer latex into the coagulating mixture in the transitionregion.
 5. The process according to claim 4, wherein flowing thecoagulating mixture comprises flowing the coagulating mixture throughthe transition region under conditions of turbulent flow.
 6. The processaccording to claim 1, wherein in step b) the coagulated latex compositeis dewatered into a desired water content of 1% to 20%.
 7. The processaccording to claim 1, comprising, before step c), a further step ofdrying the dewatered coagulated latex composite.
 8. The processaccording to claim 1, wherein in step c) the constituents arethermomechanically kneaded at a temperature between 145° C. and 185° C.9. The process according to claim 1, wherein in step d) the constituentsare worked at a temperature between 60° C. and 100° C.
 10. The processaccording to claim 1, comprising the step of calendering or extrudingthe rubber composition obtained after step d).
 11. The process accordingto claim 1, wherein the amount of the second elastomer in the compositeis from about 16 wt % to about 38 wt %.
 12. The process according toclaim 1, wherein the second elastomer is a synthetic elastomer.
 13. Theprocess according to claim 1, wherein the second elastomer latex isnatural rubber latex.
 14. The process according to claim 13, wherein thenatural rubber latex comprises field latex, latex concentrate, skimlatex, or a combination of two or more of these.
 15. The processaccording to claim 13, wherein a component of the natural rubber latexhas been chemically or enzymatically modified.
 16. The process accordingto claim 1, wherein the elastomer composite includes at least 10 phr ofthe particulate filler.
 17. The process according to claim 1, whereinthe ingredients of step c) comprise an additive selected from the groupconsisting of filler, other elastomers, other or additional masterbatch,antioxidants, antiozonants, plasticizers, processing aids, resins,flame-retardants, extender oils, lubricants, methylene acceptors ormethylene donors, coupling activators, and a mixture of any of them. 18.The process according to claim 1, wherein the rubber composition is atire tread.